1. Field of the Invention:
The present invention relates to range finding systems. More specifically, the present invention relates to systems for testing laser rangefinder systems.
While the present invention is described herein with reference to illustrative embodiments for particular applications, it should be understood that the invention is not limited thereto. Those having ordinary skill in the art and access to the teachings provided herein will recognize additional modifications, applications, and embodiments within the scope thereof and additional fields in which the present invention would be of significant utility.
2. Description of the Related Art:
Laser rangefinders are well known in the art. These systems offer highly accurate range measurements. A typical laser rangefinder may determine the range of an object at a distance of 2000 meters within .+-.5 meters.
Laser rangefinders consist of a laser which transmits of pulse of energy downrange toward a target. This pulse is reflected by the target and detected by the rangefinder. The round-trip delay of the return pulse is measured and used for the range calculation.
Laser rangefinders are precision instruments requiring testing and calibration to ensure optimum performance. Current options for testing these systems include field tests and laboratory tests.
Field testing involves use of the rangefinder to measure the range to a target which is set up at a known distance from the rangefinder. The measurement provided by the rangefinder is compared to the known range to facilitate the test. Unfortunately, field testing is inconvenient and therefore costly.
Testing in the laboratory is somewhat more convenient and less costly than field testing. Conventional laboratory testing involves the 1) use of optical fibers or 2) use of electronic circuitry.
Optical fiber based laboratory testing systems include an optical fiber of a known length which has an optical path length equal to the distance at which the measurement is to be taken. Unfortunately, the limited optical bandwidth of optical fibers precludes the ability of the system to test long wavelength lasers. For example, optical fiber testing systems have a bandwidth limited to 0.4-2.0 microns and can not be used to test carbon dioxide lasers which operate in the ten micron range.
Conventional electrical laboratory testing systems typically include a photodetector which detects the pulse from the laser rangefinder. The signal from the photodetector is delayed and used to trigger a radiation source to simulate the round-trip delay from the rangefinder to the target and vice versa. However, this system is also limited in bandwidth by the operating range of the photodetector.
Thus, a need remains in the art for an inexpensive technique for testing long wavelength laser rangefinders in a laboratory environment.